1. If you have connected sensor to the Arduino, but unable to use it, please first check the current serial port-level mode, it may be in TTL level, while our module works in RS232 levels.
2. The ultrasonic attenuation violently in the air (inversely proportional to the d²(distance)), besides, barrier surface reflection of the sound is affected by many factors (such as barrier shape, orientation and texture) the influence of ultrasonic distance measurement is therefore limited.
3. The far testing distance is a wall, close test can be a pen. Analyte based on the use of the environment and quality of different measurement may result in inconsistent with the data provided.
4. The mentioned servo above is a ordinary model on the market, can be rotated 180 degrees. If you use a special steering servo, it may draw the user's attention to control the timing in a different way.
Tonny12138 
